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Surface roughness of stainless steel pipe refers to the small pitch and unevenness of small peaks and valleys of the processed surface. The distance (wave distance) between its two peaks or two valleys is very small (below 1mm), and it belongs to the micro geometry error. The smaller the surface roughness, the smoother the surface.
Surface roughness is generally formed by the processing method used and other factors, such as friction between the tool and the part surface during processing, plastic deformation of the surface layer metal during chip separation, and high frequency vibration in the process system. Due to different processing methods and stainless steel pipe materials, the depth, density, shape and texture of the marks left on the processed surface are different.
Surface roughness is closely related to the matching properties, wear resistance, fatigue strength, contact stiffness, vibration and noise of mechanical parts, etc., and has an important impact on the service life and reliability of mechanical products. Generally, Ra is used for labeling.
Different surface roughness, see the table below.
Surface features | Surface roughness (Ra) value | Examples of processing methods |
Clearly visible knife marks | Ra100, Ra50, Ra25 | Rough turning, rough planing, rough milling, drilling |
Slightly seen knife marks | Ra12.5, Ra6.3, Ra3.2 | Fine turning, fine planing, fine milling, rough hinge, rough grinding |
No visible processing marks | Ra1.6, Ra0.8, Ra0.4 | Fine turning, fine grinding, fine hinge, grinding |
Dark glossy surface | Ra0.2, Ra0.1, Ra0.05 | Grinding, honing, super-fine grinding, polishing |
The wall roughness of stainless steel pipe usually refers to absolute roughness (ε) and relative roughness (ε / D).
Relative roughness refers to the ratio of roughness bulge height (absolute roughness) ε of pipe wall to inner diameter D of pipe, that is, ε / d.
The absolute roughness represents the average height of the protruding part of the inner wall of the pipe. In selection, factors such as corrosion, abrasion, scaling and use of the fluid to the pipe wall should be considered. For example, for seamless steel pipe, when the fluid is oil gas, saturated steam, dry compressed air and other less corrosive fluid, absolute roughness ε = 0.2mm can be selected; when transporting water, if it is condensate (with air), ε = 0.5mm can be selected; for pure water, ε = 0.2mm; for untreated water, ε = 0.3-0.5mm; for acid, alkali and other more corrosive fluid, it can be selected = 1mm or more.